In general, the answer to your question is "yes". But the practical/likely answer for you is "no".
Yes -- if you complete training in Canada, then you should be able to get a license in the US and sit for the appropriate board exam. As mentioned above, the training time for some fields is different and this can cause some problems. So you need to check carefully.
But no -- realistically, the chances of getting a spot as an IMG in Canada are very low. Most IMG's that are Canadian citizens end up doing their training in the US (where obtaining spots for IMG's is more realistic), and then return to Canada to work as US and Canadian training is interchangeable. Canada is quite strict about training time, so if training is shorter in the US you do have to find some way to get the extra training.
Getting a spot in Ophthal in general is very difficult. It takes audition rotations and connections, and as an IMG that's simply very unlikely. Getting a spot in the US in Ophthal is likewise extremely difficult -- the field is very competitive and it takes stellar scores, lots of US experience, often year(s) of research, and quite a but of luck. Getting a spot in Rads in the US as an IMG is much more reasonable, but still requies good scores and US clinical experience.
As already mentioned, getting a visa outside of training is a different beast than getting a training visa. It's much more difficult, in general. You can't just open your own private practice.
Last, even if you do your training in Canada, you might not find getting a job in the US easy. Medicine in the two countries is practiced quite differently. Billing and coding are wildly different. US programs might not be familiar with Canadian training programs.